Motors are widely used as sources to actuate mechanical components. Unfortunately, most motors are quite big, as they have many parts which are produced by conventional machining and assembly techniques. For that reason, there has recently been much research to develop MEMS micro-rotating devices, that is mechanical devices having dimensions of sub millimeters (for example, in case of a motor, having a maximum diameter no more than say 15 millimeters). Examples of such micro-rotating devices include micro-pumps or motors. However, reducing the size of the motor by reducing the size of its parts increases the difficulty in handling them, and significantly increases production cost.
Known micro-rotating devices have a rotor element which includes a sleeve and which rotates around a spindle shaft threaded through the sleeve. A typical micro-rotating device is illustrated in cross-section in FIG. 1. It comprises a rotor (rotating disc) 101 and a stator 105. The stator 105 is formed with multiple coil windings (not shown). The spindle shaft 102 extends from the stator 105, and passes through a central aperture 106 in the rotor 101. The inner surface of the aperture 106 constitutes the sleeve for the shaft 102. The rotor includes a trench on its surface facing the stator 105. The trench encircles the aperture 106 and is filled with a permanent magnet 104 and a yoke 103. The rotor 101 rotates about the spindle shaft 102 when there is a continuous flow of electrical current into the coil windings on the stator 105. The micro-rotating device of FIG. 1 is constructed by placing the sleeve of the rotor disc 101 onto the shaft 102.
In contrast to conventional motors, the known MEMS micro-rotating device has a reduced the number of parts because these are fabricated from substrates such as Si and Glass. However, there are still several parts which are required to be put together in the assembly process. For example, it is necessary to combine the shaft with the rotor when a motor is assembled. It is difficult to establish reliable processes for such assembly, because size of each part is very small.